Wired telecommunications rely on telephone lines to facilitate voice and data transmissions. Because of the proliferation of uses for telephone lines, there has been a growing concern to protect operating personnel and/or connected communications equipment from excessive voltages and currents. Excessive voltages and currents may be caused by, for example, lightning strikes, power line crosses, and/or currents induced from adjacent power lines.
Primary telecommunications protectors, at a minimum, provide overvoltage protection. This is typically done with at least one protection element that is inserted between a conductive tip element of a surge protector and ground. Likewise, typically at least one protection element is inserted between a conductive ring element of the surge protector and ground. When a hazardous overvoltage is present on a line, the overvoltage protection element changes from a high impedance to a low impedance state, effectively shorting the hazardous overvoltage and its associated overcurrent to ground and away from equipment and/or personnel.
There are occasions when an excessive current may be present with no overvoltage. This is typically called a “sneak current” and may occur when there is AC induction on the line or when the tip and ring conductors are somehow shorted, or nearly shorted, to ground. During such a condition, the overvoltage protection element may not short to ground, thereby allowing hazardous overcurrents to pass by the protector to the equipment and/or personnel. Over time, the sneak current condition may cause excessive damage to the telecommunications equipment.